CRED Optical Validation Data at Howland Island in the Pacific Remote Islands Area (PRIA), 2002, to Support Benthic Habitat Mapping

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What does this data set describe?

Title:
CRED Optical Validation Data at Howland Island in the Pacific Remote Islands Area (PRIA), 2002, to Support Benthic Habitat Mapping
Abstract:
Optical validation data were collected using a Tethered Optical Assessment Device (TOAD), an underwater sled equipped with an underwater digital video camera and lights. Data were collected at Howland Island to support Benthic Habitat Mapping efforts during NOAA Ship Townsend Cromwell cruise TC0201.
Supplemental_Information:
Howland, a low-lying 1.84 sq.km. island in the Pacific Remote Island Area (PRIA), is the northernmost of the Phoenix Islands. Centered at 00 degrees 48N, 176 degrees 38W, it is within one degree latitude of the equator. It lies within an arid zone of the tropical Pacific, with insufficient groundwater and rainfall to support continuous human habitation. Although Howland was unhabited at the time of its discovery by Western sailors, Polynesians probably visited it periodically over many centuries to harvest fish and wildlife. The lack of human habitation allowed Howland's coral reefs to remain completely pristine until the early 20th century. Even today it lies beyond the influence of urban centers, associated pollutants and major shipping lanes. In 1857, Howland was claimed by the U.S. under the Guano Act. A short-lived colonization attempt was made between 1935 and World War II, but was abandoned thereafter. The famed American aviatrix Amelia EARHART disappeared while seeking out Howland Island as a refueling stop during her 1937 round-the-world flight; Earhart Light, a day beacon near the middle of the west coast, was named in her memory. A no-take island and marine protected area National Wildlife Refuge administered by the U.S. Fish and Wildlife Service, Howland is under the joint jurisdiction of the Departments of Interior and Commerce. Ocean currents transport and distribute larvae among and between different atolls and islands, and particularly in the Pacific equatorial region, define sea surface temperatures (SSTs) and available nutrient regimes. The North Equatorial Current (NEC), Equatorial Counter Current (ECC), Equatorial Undercurrent or Cromwell Current (EUC), and South Equatorial Current (SEC) provide the mechanism by which many species are distributed among the PRIAs, nearby central Pacific islands, the main Hawaiian Islands (MHI), as well as other distant regions.

Optical validation data were collected using the Tethered Optical Assessment Device (TOAD), a sled equipped with underwater video camera, still camera, and lights. These data are used to provide ground-truth validation that for benthic habitat maps based on multibeam echosounder surveys. Camera sled deployments were conducted at night, usually between 1800 and midnight. The TOAD was deployed from a pot hauler mounted on the starboard side of the fantail on NOAA Ship Townsend Cromwell. It was lowered slowly to the bottom by the deck crew with the use of a capstan. The TOAD operator monitored a live video feed from the camera and began recording data on two video tape recorders. When the camera reached bottom the deck crew was notified by radio to stop lowering. The TOAD was a MiniBat 8820 unit manufactured by Guideline, and was towed by the ship at 1-2 knots while remotely guided from the ship using adjustable wing controls to keep the unit close to the underwater substrate. The TOAD was damaged during the cruise on 02/20/02, and subsequent tows were conducted as drift deployments. At each station the ship was positioned with the wind on the starboard side and drifted downwind; occasional light turns were applied to the ship's screws if necessary to reduce the ship's motion. The operator continued to monitor the vehicle and provided commands to raise or lower it to keep the camera just above the bottom.

Equipment Description: The TOAD is a camera sled based on the Guildline MiniBat model 8820 tow body. The frame was configured with a single Sony DCR-PC110 Digital Video Camera in a modified Gates underwater housing, a Canon Power Shot G1 Still Camera (modified by CRED engineers) in an Ikelite housing rated to 60 m slaved to an Ikelite DS-50 strobe, and two 500 W DeepSea Power & Light model 710-0400601 underwater lights. The Canon camera had a custom-built timer that enabled the user to select a constant time interval (ranging from approximately 5 seconds to 2 minutes) between photographs. An interval of 30 seconds was typically selected, which, assuming a mean velocity for the camera sled of of 1.5 knots, resulted in one photograph approximately every 20 m. Photograph resolution is 2048 x 1536 pixels and file names are assigned sequentially and automatically by the camera, starting at 100-0000 after the camera's memory is cleared. The MiniBAT pressure sensor and wing controller were also mounted on the frame but the pressure sensor was not operational. After damage to the TOAD on 02/20/02 and the sled's wings were not installed thereafter. The cable between the sled and the surface was an underwater load-bearing electrical cable. The TOAD computers were located in the Electronics Lab of the Townsend Cromwell. The electronics box containing the power switches was secured to the ship's fantail, and all other TOAD surface components were secured in the ship's wet lab.

Name and address of person collecting data: Joyce Miller & Ron Hoeke NOAA IRC NMFS/PIFSC/CRED 1845 WASP Blvd., Building 176 Honolulu, HI 96818

Data Files: Video data were recorded on two video tape recorders. Still photos were recorded on digital camera and downloaded to the TOAD computer after the tow. The position of the camera sled was recorded using Guildline MiniBat In-Tow data acquisition software.

File naming convention: Each tow is given a name consisting of a three-letter designator for the island area, followed by a two-digit year and a three-digit tow number, which increments by one for each new tow around that island. During OES0402 (NOAA Ship Oscar Elton Sette's 2nd cruise in calendar year 2004) the consecutive tows at Tutuila started at TUT04000. For following cruises, the tow numbers will increment by 100, so the first tow on the next cruise to Tutuila in 2004 will be tow number TUT04100. Video tape labels, the navigation files (*.glo) and paper log forms are annotated with the tow name and number, e.g., TUT04012. If the navigation file is edited during processing the file name has a suffix 'a' added. For example, for a navigation data file named TUT04012a.glo, the 'a' would indicate that metadata were extracted from the navigation data and recorded to a file with the same name as the navigation file except that a file type of '.met' was appended; for example, 'TUT04012a.glo.met.

Time Correlation: All times are based on UTC. Two clocks were set manually synchronized prior to starting data collection; the clock in the video character generator that was used to annotate the video tape and the TOAD data acquisition computer clock was used to annotate the navigation (*.glo) files. These clocks were set to UTC at the beginning of each evening's operations and then compared to one another prior to (and during) each tow. There were problems maintaining synchronization of the TOAD computer clock during this cruise. See the problems section for a description.

Resource Description: Digital video images that are geo-referenced to navigation files.

  1. How should this data set be cited?

    Pacific Islands Benthic Habitat Mapping Center (PIBHMC), Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), 200704, CRED Optical Validation Data at Howland Island in the Pacific Remote Islands Area (PRIA), 2002, to Support Benthic Habitat Mapping.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -176.64
    East_Bounding_Coordinate: -176.60
    North_Bounding_Coordinate: 0.84
    South_Bounding_Coordinate: 0.78

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 29-Jan-2002
    Ending_Date: 01-Feb-2002
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form:
    Video and photo imagery, track line navigation files, and log sheets

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

    2. What coordinate system is used to represent geographic features?

  7. How does the data set describe geographic features?


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    Pacific Islands Benthic Habitat Mapping Center, Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), NOAA

  3. To whom should users address questions about the data?

    Pacific Islands Benthic Habitat Mapping Center (PIBHMC), Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA)
    Attn: John Rooney
    NOAA IRC
    Honolulu, HI 96818

    808 725-5360 (voice)
    808 725-5429 (FAX)
    nmfs.pic.credinfo@noaa.gov

    Contact_Instructions: e-mail preferred


Why was the data set created?

These data provide optical observations that will be correlated with bathymetry and acoustic backscatter imagery to develop a benthic habitat map of Howland. Refer to supplemental information for description of instrument and survey.


How was the data set created?

  1. From what previous works were the data drawn?

  2. How were the data generated, processed, and modified?

    Date: 17-Nov-2005 (process 1 of 1)
    After a tow was completed the video tape data was reviewed by spot-checking the master and backup tape to verify that data were recorded. Navigation data were copied from the acquisition computer to the data archive. A metadata extractor (glofilter.py, version 3/17/06) was run to summarize the navigation data and test for errors. If errors were detected in a record, a copy of the data file was made (the 'a.glo' file mentioned above), that record was automatically flagged as invalid, and corrections were made if possible. This file's header was updated to document what type of processing occurred. A metadata file was recorded in the data archive in the same location as the navigation data. Processed navigation data were then imported to ArcGIS 9.x.

    Still photographs, collected every 30 seconds and averaging approximately 20 m horizontal spacing between them, were analyzed using a point count method. Five circles approximately 0.5 mm in diameter and spaced equidistantly were drawn in a horizontal line on a piece of clear plastic sheet taped to a computer monitor screen. Within the center of each circle the substrate (rock, sand, rubble, etc.) living cover (seagrass, scleractinian [stony] coral, macroalgae, etc) and growth morphology of coral colonies (branching, encrusting, etc) were identified. Classification information was recorded on a spreadsheet for each camera tow according to the codes described in the file BenthicHabitatClassificationCodes_Metadata.xls. The substrate within the first circle is recorded under the column labeled S1 while the living cover and coral growth morphology within the same circle are recorded under the columns labeled C1 and CM1. Data from the second circle are recorded under columns S2, C2, CM2, and so on.

  3. What similar or related data should the user be aware of?


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

    The horizontal position accuracy for the camera sled position is 100 meters. There are three primary sources of this error. The ship's positioning is based on GPS SPS, often called standalone or non-differential GPS positioning. SPS has a measured accuracy of under 5 meters. The position of the GPS antenna is used; no attempt is made to translocate this position to that of the tow block from which the camera is deployed. The difference between the tow block and the antenna is about 14 meters. The camera sled position is based on a layback calculation that use ship's course, the amount of cable out and the camera sled depth to develop an estimate of the camera sled position. The amount of cable deployed is manually entered by the operator during a given camera tow.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Complete

  5. How consistent are the relationships among the observations, including topology?

    Unspecified


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints:
Please acknowledge the NOAA Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center as the source of this information.

  1. Who distributes the data set? (Distributor 1 of 1)

    Pacific Islands Benthic Habitat Mapping Center (PIBHMC), Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA)
    Attn: John Rooney
    NOAA IRC
    Honolulu, HI 96818

    808 725-5360 (voice)
    808 725-5429 (FAX)
    nmfs.pic.credinfo@noaa.gov

    Contact_Instructions: e-mail preferred
  2. What's the catalog number I need to order this data set?

    Offline Data

  3. What legal disclaimers am I supposed to read?

    These data are not to be used for navigational purposes. NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 12-Mar-2014
Metadata author:
Pacific Islands Benthic Habitat Mapping Center (PIBHMC), Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA)
Attn: CRED Data Management Team
NOAA IRC
Honolulu, HI 96818

808 725-5360 (voice)
808 725-5429 (FAX)
nmfs.pic.credinfo@noaa.gov

Contact_Instructions: e-mail preferred
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)


Generated by mp version 2.9.13 on Sat Oct 25 10:43:10 2014